Getting rusty?

gajinoz

gajinoz

Joined
Sep 2, 2003
Messages
11,650
There has been a bit of discussion on another forum, (no, not THE "other" forum, just another forum), about coated blades and corrosion appearing under the coating.

Have you ever picked up your coated blade to use it or sharpen it or clean the crap out of your toenails or whatever and discovered the coating coming off and, shock, horror, corrosion on the blade?

I'd be interested to hear about any such discoveries.
 
My knives have to take off their coats when they come inside.

OK, OK, seriously ... since I do have a few coated blades, no: I haven't noticed corrosion under the coats,
although I have wondered about handles. I had a small necker with rust under the handle.
 
gajinoz said:
There has been a bit of discussion on another forum, (no, not THE "other" forum, just another forum), about coated blades and corrosion appearing under the coating.

Have you ever picked up your coated blade to use it or sharpen it or clean the crap out of your toenails or whatever and discovered the coating coming off and, shock, horror, corrosion on the blade?

I'd be interested to hear about any such discoveries.
Click to expand...

It hasn't happened to me, but the only 2 coated blades I've used extensively both use Kershaw's black DLC (Diamond Like Coating). One was a combo-edged Kershaw Blackout (used for a couple of years with no coating degradation or corrosion...since misplaced), and the other, in my current EDC rotation, is a combo-edged Kershaw Tactical Blur. It's stood up so far to a year of heavy use without any ill effects. I would think that if this process were going to occur at all, it would do so around the serrations which I tend to use to tackle the really tough jobs, but it hasn't.

I have a number of coated blades put away as part of my collection, all of which have remained pristine, but they've all had some type of protectant routinely applied (currently Tuf-Glide). Of course the users also get this same treatment...:D

Ray :)
 
Are you asking about ss or carbon blades? I believe both that Ray described are ss...

Ray I too have had good luck with Kershaws DLC, tough stuff! I wish Spyderco used it on their belt clips. :)
 
Strigamort said:
Are you asking about ss or carbon blades? I believe both that Ray described are ss...
Click to expand...


I'm making the, no doubt, wild assumption that "stainless" blades would be unlikely to suffer this problem and it would be mostly restricted to the carbon types.
 
Strigamort said:
Are you asking about ss or carbon blades? I believe both that Ray described are ss...

Ray I too have had good luck with Kershaws DLC, tough stuff! I wish Spyderco used it on their belt clips. :)
Click to expand...

Correct you are about the stainless steel...although high-carbon stainless does corrode if not cared for...

Ray :)
 
I've never had that happen. But I've had moisture get under the handle scales, which is why it's good to have the thing coated under the scales as well.
 
Oh, stainless can have that problem too. A good buddy takes his BO Leatherman with him when we go surf fishing, and doesn't always wash it off. He's noticed some coating coming off over rust spots. At the edge only I believe.

On a related note, many people who go ocean fishing of Oregon and Washington with their sled boats affix a lump of zinc at the back of the boat under the water line. The theory goes that the zinc will attract some of the corrosion away from the hull of the boat and the motor. They often use terms like "bad juju" and so on. I've even met guys who carry a lump of zinc in their pocket. If you are superstitious about your coated knives, maybe buy yourself a lump of zinc and carry it in your pocket; it won't do you a lick of good, but you'll have a fun story.
 
I recall reading an article about Kahr pistols, a company that impresses me as being very quality and 'state-of-the-art' concious, so to speak. The Kahr guy said that they had been getting requests for a black version of their guns from LE people. They tested many coating options, and decided on DLC. The guy said that most available coatings were soft and thus easily scratched. Once a scratch goes all the way thru to bare metal, the metal is no longer protected, and can rust. Then the rust will work it's way under the coating.

They choose DLC for its hardness. I think titanium nitride is also quite hard and so should be good. It would be interesting to hear from Kershaw why they largely switched from ti-ni to DLC, especially for their high-end folders. I've had both blued and parkerized stuff rust, but never DLC, though admittedly most of the DLC coated stuff is stainless steel to begin with.
 
gajinoz said:
....

Have you ever picked up your coated blade to use it or sharpen it or clean the crap out of your toenails or whatever and discovered the coating coming off and, shock, horror, corrosion on the blade?...
Click to expand...

nope can't say i have gajinoz, i'm usually using a Victorinox Classic to clean the crap out of my toenails/ toejam and such.....stainless Rastafrei steel :thumbup:
 
bobofish - Not sure if you're aware, but it's not just a superstition and the zinc doesn't "attract" corrosion per se. Obviously carrying zinc is just a superstition, but as far as the boat is concerned, the zinc is acting as a "sacrificial anode". Being more reactive than the steel/iron, the zinc will give up its electrons and be oxidized, rather than the steel/iron. It's also used for underground pipes and various metal structures.

http://en.wikipedia.org/wiki/Sacrificial_anode
 
I recall reading that a few years back about aluminum. For a while, when I put steel items into storage I would faithfully throw in some aluminum filings wrapped in gauze, along with silica gel packs. I had forgotten about that until I read your post.
 
wutitiz said:
I recall reading that a few years back about aluminum. For a while, when I put steel items into storage I would faithfully throw in some aluminum filings wrapped in gauze, along with silica gel packs. I had forgotten about that until I read your post.
Click to expand...

Two problems with that. Aluminum does not work well as a sacrificial anode at neutral pH, which you would have in a standard storage area. Also, a sacrificial anode has to be in direct electrical contact with the metal being protected. The zinc plates on boats are electrically bonded to all the major metal items on the boat.

Meanwhile, back to the thread.
Coated blades will be more prone to corrosion than blades with black oxide or other inorganic layers. As for examples, I have none. I have a couple of Parkerized blades, no painted ones.
 
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